Re: Give MonadTrans a QuantifiedConstraints superclass
Henning Thielemann <[email protected]>
| Newsgroups | gmane.comp.lang.haskell.libraries |
|---|---|
| Message-ID | <[email protected]> |
On Wed, 2 Jun 2021, Baldur Blöndal wrote: > This is to advertise the proposal > (https://gitlab.haskell.org/ghc/ghc/-/issues/19922) to add a > superclass to the MonadTrans type class in Control.Monad.Trans. > > A Monad transformer 'trans' lifts a 'Monad m' to a 'Monad (trans m)'. > > This proposal code-ifies that with a superclass constraint: > > class (forall m. Monad m => Monad (trans m)) => MonadTrans trans where > .. > > This is the main motiviating example of the Quantified Class > Constraints paper https://gkaracha.github.io/papers/quantcs.pdf So far, 'transformers' is mostly Haskell 98. This is why I prefer it to 'mtl'. Wouldn't it be enough to add this extension to 'mtl'? I see that 'mtl' re-uses the MonadTrans class from 'transformers' but maybe it should define its own class with the quantified constraints then. _______________________________________________ Libraries mailing list [email protected] http://mail.haskell.org/cgi-bin/mailman/listinfo/libraries